214 LEAF-MINING INSECTS 



has some dorsal markings also. On the ventral side spots 

 are common at least on the thoracic segments. In mining, 

 the venter is uppermost, sheltered only by the leaf's thin 

 cuticle, and these spots perhaps protect the nervous ganglia. 



These sawflies moult six times as larvae, five times in the 

 leaf and a sixth upon going into the pupal state. The five 

 moult skins are usually to be found in the mine. Instead of 

 finding the head capsule in one place and the body covering 

 in another, as in lepidopterous miner moults, these are 

 wont to be in one piece, with a slit through the vertex of the 

 head capsule and through the prothoracic shield. In 

 moulting the head and thorax are first worked out through 

 the slit and then by a series of wriggling movements the 

 shell is worked down the body and off the anal segment. 

 The thin body cuticula beyond the prothoracic shield may 

 be turned partly inside out in the process or is at least very 

 much drawn and wrinkled. 



Except in size and the increasing visibility of appendages 

 the larvae change but little from instar to instar until the 

 sixth. The head capsule becomes slightly more oblique by 

 the fourth and fifth instars. In the sixth instars the head 

 capsule becomes vertical. The larvae are now less depressed 

 and moniliform and are usually without spots of any kind. 

 In this stage they do not feed but members of the Fenusinae 

 and Scolioneurinae break through the upper cuticle of the 

 mine, crawl to the edge of the leaf fall to the ground, enter 

 the earth to a depth of not more than a few inches, and there 

 make a slight cocoon of silk and particles of earth. If some 

 of the cocoons be sifted out of the earth in the months after 

 the larvae have entered the ground (and these are hard to 

 discover even in breeding boxes where the quantity of earth 

 is small and the larvae are known to be present) they will 

 be found to contain white inert larvae with the head bent 

 forward and the thorax somewhat humped. In this state 

 they continue for the greater part of a year. Compound 



